Question 71
On a square board with $m$ rows and $n$ columns, where $m \le n$, some squares are colored black in such a way that no two rows are alike. Find the biggest integer $k$ such that for every possible coloring to start with one can always color $k$ columns entirely red in such a way that no two rows are still alike.
Answer: $n-m+1$.
Answer: $n-m+1$.